Well known for their role in inflammation and allergy response, mast cells are possible new players in the regulation of behavior. Mast cells have been recognized for their multifunctional character due to their occurrence in various tissues in both health and disease, and for their astute responsiveness to a changing microenvironment. Their wide functionality is reflected in their capacity to store and release a plethora of effector molecules, ranging from biogenic amines, proteases, and cytokines to small messengers such as ATP and NO. Immocytochemical studies have revealed gonadotropin-releasing hormone (GnRH) immunoreactivity in brain mast cells of rats, mice and doves. To elucidate the role of mast cells in the brain I will determine: (1) the changes in mast cell expression of GnRH during mating behavior, (2) the source of GnRH in mast cells, and (3) the effects of mast cell-neuronal interactions on the activity of neurons in the brain. The research methods applied will encompass protein and gene expression studies and calcium imaging techniques. I anticipate this work will further our understanding of cellular and molecular mechanisms underlying neuroendocrine-immune interactions, thereby allowing for advancements in current treatment strategies of related health disorders.